In many modern generators the stator coil includes conductors separated and wrapped with a tape, e.g. a mica tape. This assembly is impregnated with a resin insulation that removes air, gas, and moisture, to provide a void-free insulation. In some generators the coil is impregnated first and then assembled to the core. In other generators the coil and core are assembled first, and the entire assembly is impregnated with the resin in a process to form a monolithic stator assembly. An example of this process is Global Vacuum Pressure Impregnation (GVPI). In a GVPI process the stator assembly is processed in an alternating vacuum and pressure environment that ensures uniform distribution of resin throughout the assembly. The resin is cured to form the monolithic stator assembly. Benefits of GVPI include improved structural strength and improved resistance to moisture and chemicals etc.
When a stator rewind is necessary, where the stator coils must be removed and replaced, each coil must be removed from a slot within the stator. The coil is resin bonded into the slot, and the bond is necessarily strong. Conventional practice has been to engage the end windings of the coil and to pull them upward out of the slot with enough mechanical force to extract the coil. However, this leaves a lot of the resin still bonded to the surface of the slot, and a subsequent operation is necessary to remove the residual resin from the surface of the slot. This subsequent operation is labor intensive and time consuming.